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A general model for the zone control chart is presented. Using this model, it is shown that there are score vectors for zone control charts which result in superior average run length performance in comparison to Shewhart charts with common runs rules.A fast initial response (FIR) feature for the zone control chart is also proposed.Average run lengths of the zone control chart with this feature are calculated. It is shown that the FIR feature improves zone control chart performance by providing significantly earlier signals when the process is out of control.

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In this paper we address the problem of estimation of the common location parameter of several exponential distributions. We assume that the scale parameters are all unknown and possibly unequal. From a decision theoretic point of view we suggest a wide class of estimators dominating the maximum likelihood estimator (MLE) under a class of convex loss functions.